In wireless communication, efficient use of the available power is one of the main goals of system design. Often, a wireless local area network (WLAN) device, such as in Internet of Things (IoT) applications, relies on a limited power supply (e.g., as supplied by rechargeable or non-rechargeable batteries). Examples of such a device may include sensor devices located in remote fields measuring some physical phenomenon, e.g., water level or temperature; and wearable devices measuring some bodily function, e.g., pulse rate.
Such a device may be designed to operate on a low duty cycle (e.g., communicating with an access point (AP) only once per day) and thus it may not be appropriate for its main WLAN receiver circuit to be always on. The limited power supply (e.g., battery) of the device may be quickly exhausted if not provided with an appropriate sleep mode for the WLAN receiver circuit and an appropriate wake-up mechanism. The wake-up mechanism may involve transmission of a wake-up signal from the AP to the device and from the device to the AP.
In an environment where legacy devices that are not wake-up-enabled operate in overlapping coverage areas with wake-up enabled devices it may be beneficial that the wake-up signal be easily identifiable by such legacy devices as a non-valid signal.